The aims of the proposed work are: Firstly, to investigate the mechanism of physiological adaptation of Na ion fluxes in the epidermis of isolated frog skin to changes in the (Na ion) of the solution at the epidermal side of the skin. Secondly, to investigate whether the adaptation response is sensitive to environmental factors, such as: temperature; osmolarity; the chemical nature of the anion; to Ca ions, K ion, H ion; to drugs and hormones, especially to catecholamines. Thirdly, to interpret the results by computer simulation, applying a multicompartmental flow system resembling the fine structure of the epidermis. The rationale behind this work is, that the results may shed new light on the pathways which Na ion travels across the epidermis in influx and outflux. Both intact belly skin of Rana pipiens, and stripped epidermis will be used. The tissue membranes will be short-circuited in the classical double chamber, with modifications as needed. Besides taking the usual electrical measurements, data will be collected for calculations of transient and steady state rates of Na ion influx and outflux, and of steady state Na ion pool sizes.